1. Field of the Invention
The present invention relates to antimicrobial polymer latexes and the antimicrobial coating, adhesive, sealant and elastomer (CASE) materials derived therefrom, wherein the polymer latex is derived from various monomers and antimicrobial quaternary ammonium ethylenically unsaturated compounds. These antimicrobial quaternary ammonium ethylenically unsaturated compounds are generally derived from ethylenically unsaturated sulfonic, phosphoric and/or carboxylic acids or salts thereof, and substantially saturated antimicrobial quaternary ammonium compounds. More specifically, the invention relates to improved antimicrobial polymer latexes and CASE materials, which possess prolonged antimicrobial activity, wherein the polymers and resulting CASE materials are produced using emulsion polymerization processes which utilize antimicrobial quaternary ammonium ethylenically unsaturated compounds derived from substantially saturated antimicrobial quaternary ammonium compounds and ethylenically unsaturated alkylsulfonic acids, alkylbenzene sulfonic acids, alkyl olefin sulfonic acids, alkyl alcohol sulfuric acid esters, or alkoxylated alkyl alcohol sulfuric acid esters, fatty acids, and fatty phosphate acid esters, or salts thereof, or mixtures thereof
2. Description of the Related Art
The emulsion polymerization of ethylenically unsaturated monomers to form discrete solid polymeric particles for use in coating, adhesive, sealant, and/or elastomer (CASE) applications is well known to the art. Surfactants are commonly used materials in the manufacture of polymer latexes and various CASE products, such as, for example paints, printing inks, adhesives and pressure-sensitive adhesives. These surfactants are often indispensable for the manufacture and/or stabilization of these products in terms of processability. However, after such CASE products are used for coating, printing, adhesion or pressure bonding, the surfactants are no longer necessary, nor desirable. Rather, if the surfactant remains in the CASE product, the surfactant tends to adversely affect the resistance of the CASE material to water and even oil in many instances.
Surfactants for use in emulsion polymerization to form latexes, which are then used to prepare CASE materials, include traditional anionic surfactants, such as sodium dodecylbenzenesulfonate and nonionic surfactants such as polyoxyethylene nonylphenyl ether. However, CASE materials using polymer latex emulsions prepared using such traditional surfactants have the drawbacks of poor resistance to water and poor bond strength, typically because the surfactant remains in free form in the polymer latex and/or final CASE material. Additionally, these CASE materials often possess little or no antimicrobial activity, absent the addition of a separate antimicrobial material. When CASE materials are formulated to include such an antimicrobial material, the antimicrobial activity of the CASE material decreases realtively quickly with the passage of time and upon repeated exposure of the CASE material to various elements, including for example, water, washings with cleaning products, UV light, and the like.
CASE materials typically comprise, for example, paints (high-gloss, semi-gloss, and flat), caulks, and the like. CASE materials are typically applied to a variety of substrates, including for example, wood, metal, plastic, glass, ceramics, fiberglass, composite materials, cardboard, corrugated board, paper, textiles, non-woven materials, plastic, foam, tape or a combination thereof. Substrates can be virgin materials, i.e. materials which have not previously be treated or coated with a case material, or materials which have been previously coated or treated with a CASE material. CASE materials can be applied on top of or applied to a previously applied CASE material.
Conventional emulsion polymerization of ethylenically unsaturated monomers employs one or more surface active materials to emulsify the monomers and to stabilize the resulting polymer products, i.e., the latex. The monomers used in emulsion polymerization reactions are generally water-insoluble, but in some cases may be water-soluble. During a typical emulsion polymerization, a surfactant is used to suspend small portions of monomer in a continuous or a semi-continuous aqueous phase. Typically, the monomer molecules are dispersed or suspended as small spheres in the aqueous phase, wherein the polymerization takes place within the small spheres. The surface active agents, i.e., surfactants, typically utilized in emulsion polymerization reactions are anionic, nonionic, and cationic surfactants or a mixture thereof.
The polymeric particles formed by the emulsion polymerization process are typically utilized to prepare coating, adhesive, sealant, and/or elastomer (CASE) materials. In a traditional emulsion polymerization reaction, the surfactant does not become chemically bonded to the polymeric particles by carbon-carbon bond formation, but rather remains absorbed on the polymeric particle product solution after the emulsion polymerization reaction is complete, i.e., once all of the monomer(s) is reacted. The unreacted surfactant can have a detrimental effect on the polymer product solution, as it can interfere with the performance of such polymerization products in CASE materials; the suspension of polymeric particles may become destabilized over time and undergo unwanted coagulation. In addition, the unreacted surfactant does not provide any desireable antimicrobial activity to the CASE material. The unreacted surfactant may cause unwanted peeling of a latex paint coating on a substrate, and decreased moisture and scrubability resistance in other various CASE applications. Residual surfactant can cause an undesirable xe2x80x9cbloomingxe2x80x9d that leads to surface irregularities in a resulting CASE material that is applied to a substrate. Additionally, residual surfactant may lead to undesirable decreases in adhesion of a particular CASE material. The traditional surfactants act as stabilizers before, during, and after polymerization, but they typically have a detrimental effect on the properties of a dry latex film, for example, due to their tendency to migrate, i.e., to leave their original positions at the latex particle surfaces and form areas of higher concentration both in pockets within the film and at the film/air and film/substrate interfaces.
Several proposals have been made in the prior art to employ a polymerizable surfactant as the surface active agent during an emulsion polymerization reaction. U.S. Pat. No. 5,478,883 (incorporated herein by reference in its entirety) describes the use of ethylenically unsaturated polymerizable water-soluble nonionic surfactants formed by the reaction of a diallylamine compound with ethylene oxide, propylene oxide or butylene oxide, in emulsion polymerization reactions. Similarly, U.S. Pat. No. 5,162,475 (incorporated herein by reference) provides alpha-beta ethylenically unsaturated poly(alkylenoxy) polymerizable surface active compounds for use in emulsion polymerization. For additional examples of polymerizable surfactants for use in emulsion polymerization processes, see U.S. Pat. Nos. 4,377,185 and 4,049,608. Also see WO8912618, EP 747456 A2, and EP 770655 A2; all describing various ethylenically unsaturated surfactant approaches to producing CASE materials with reactive surfactants. However, none of these approaches have provided an alterative to improving the CASE material and at the same time, made the polymer latex and/or the resulting case material antimicrobial, i.e. resistant to bacteria, fungi, algae, viruses, and the like.
Non-polymerizable surfactant solutions to the traditional problems encountered in performing an emulsion polymerization process are numerous. U.S. Pat. No. 3,941,857 describes the use of epoxy resins which react with the residual anionic, cationic or nonionic surfactant. Polymerizable compounds such as allyl alcohol (and esters thereof) have been found to be ineffective due to the formation of undesirable high levels of coagulum in the final emulsion polymerization product. Additionally, see U.S. Pat. Nos. 4,224,455; 5,399,617; 4,075,411; 5,344,867; 5,296,627; 5,679,732, 5,536,811; 4,912,157; and 5,039,339; and WO 97/45495.
Quaternary ammonium salt formulations have been used as disinfectants for many years and these formulations have broad spectrum antimicrobial activity. These formulations are effecatious, at higher concentrations of quaternary ammonium salts, against certain gram positive and gram negative bacteria. These formulations have also been shown to show tuberculocidal activity. These formulations have been incorporated into latex formulations to prepare a blend of latex polymer particles and quaternary ammonium compounds, wherein the resulting formulation is applied to a substrate as a CASE material. These CASE materials and the substrates treated with the CASE materials often posses excellent initial antimicrobial activity. However, upon the passage of time, exposure to the elements, exposure to water, or repeated washings, the antimicrobial activity of the CASE and/or substrate decreases. This is generally due to a washing away or removal/leaching of the quaternary ammonium compounds present in the CASE material since these quaternary agents migrate to the surface.
It is known that on the surfaces of most substrates, micro-organisms develop grow, reproduce and or thrive. These micro organisms consist of a of organic materials, bacteria, algae, protozoa or other microorganisms, depending on the substrate and the type of exposure to the enviroment of the substrate. Numerous compounds termed biocides have been proposed and used for the treatment of such substrates to kill the micro organisms. Those most commonly employed in practice are halogens or halogenated inorganic or organic derivatives, such as chlorine, bromine, iodine, potassium chloride, hypochlorous acid and its sodium or calcium salts, hypobromous acid, the salts of dichloro- and trichloroisocyanuric acids, or halogenated hydantoins; however, these compounds have the disadvantage of being corrosive and of forming chlorinated compounds which are highly toxic. It has also been proposed to use peroxygenated derivatives, phenols and phenol derivatives, heavy metals or organic derivatives thereof, formaldehyde, benzoic acid and benzoates for treatments by contact with a substrate. However, many of these compounds are expensive, and/or they leave toxic or corrosive residues on the substrate. Generally, in order to be suitable for use in an appropriate fashion in a process for the treatment of microorganisms on a substrate, a biocidal compound must have the properties of: preventing the formation of the biological micro organisms, low toxicity to humans and animals that may come in contact with the biocidal compound and/or the substrate treated with such compounds, high fungicidal, algicidal and bactericidal activity.
Thus, there is a need for emulsion polymerization latexes and processes to prepare latexes comprising polymers and discrete polymeric particles that are well suited for use in antimicrobial CASE applications. There is a specific need for antimicrobial polymer latexes and CASE materials which comprise the polymer latex, wherein the final CASE material possess low water sensitivity, improved scrubability and/or improved adhesion properties. Additionally, improved antimicrobial CASE materials with prolonged antimicrobial activity, low animal toxicity, increased latex shear stability and lowered film yellowing tendencies are highly desirable. As will be more fully described hereinafter, it has been surprisingly discovered that incorporating antimicrobial quaternary ammonium compounds into the polymer latex particles by carbonxe2x80x94carbon bond formation provides an antimicrobial latex polymer which can subsequently be used to prepare antimicrobial CASE materials with prolonged antimicrobial activity, The antimicrobial activity remains even after the CASE materials and the substrates treated with the CASE materials are repeatedly exposured to the elements, exposured to water, or repeatedly washing many times; i.e., the antimicrobial activity of the CASE and/or substrate remains high for an extended period of time and there is generally no washing away or significant removal/leaching of the quaternary ammonium compounds present in the CASE material.
The present invention relates to antimicrobial polymer latexes and polymer solutions and CASE materials prepared from such materials, wherein the latexes and solutions are formed using a variety of monomers in combination with a group of compounds in the form of quaternary ammonium ethylenically unsaturated compounds derived from ethylenically unsaturated sulfonic, phosphoric and/or carboxylic acids or salts thereof, or mixtures thereof, and substantially saturated quaternary ammonium compounds, wherein the quaternary ammonium ethylenically unsaturated compounds display both surface activity, i.e. they are surfactants, and antimicrobial activity. The polymer latexes, and resulting antimicrobial CASE material produced therefrom, generally possess antibacterial activity (e.g., gram negative and gram positive bacteria). These materials may also act as fungicides, mildewcides, tuberculocides, mycobacterialcides, viralcides, and the like. It has been discovered that improved antimicrobial CASE can be prepared using such antimicrobial latexes based on these antimicrobial quaternary ammonium ethylenically unsaturated compounds which function as reactive surfactants, i.e. surface active agents in polymerization processes, particularly emulsion polymerization processes. The antimicrobial CASE materials of the instant invention are based on antimicrobial quaternary ammonium ethylenically unsaturated compounds (surface active agents) which are generally capable of co-polymerizing with other ethylenically unsaturated monomers of the type which are commonly employed in polymerization processes. The polymerizable surface active agents utilized in the present invention are prepared from readily available, economical raw materials, and generally, their preparation does not require any special handling or equipment. These polymerizable surface active agents are particularly well suited for use in the formation of polymer particles which in turn may be used to prepare a variety of antimicrobial CASE materials. Surprisingly, these materials impart prolonged antimicrobial activity to the CASE materials and may also improve many of the properties of various antimicrobial CASE materials, such as for example, improved water sensitivity (i.e. they become more hydrophobic), improved scrubability, improved adhesion, increased latex shear stability, lowered film yellowing tendencies, decreased paper discoloration, and improved wet strength in paper coatings.
Examples of antimicrobial CASE materials of the instant invention include, among others, interior and exterior coatings, e.g., latex paints, container, paper and paperboard coating, e.g., can coatings, adhesives, such as water-born adhesives and pressure sensitive adhesives, sealants, industrial coatings, waxes, automotive coatings, textile coatings and binders, floor finishes, water-based inks, films, and binders and coatings for non-woven materials such as carpet backing.
The polymerizable surface active agents utilized in the instant invention may be prepared in a batch mode or a continuous mode. They may be prepared by contacting the ethylenically unsaturated acid, or a salt thereof, with a substantially saturated quaternary ammonium compound, or vise versa. The result of such contacting typically produces acid and/or salt formation, whereby such acid and/or salt may be removed by a variety of techniques know to those skilled in the art, including for example, extraction, filtration, distillation, or a combination thereof. By contacting it is meant that the ethylenically unsaturated acid(s) or salt(s) is added to the substantially saturated quaternary ammonium compound, or vise versa, and the components are mixed to effectuate the formation of an ethylenically unsaturated quaternary ammonium compound and and acid(s) or salt(s). Typically, upon mixing, the proton, or cation of the acid salt (i.e. ammonium, sodium, magnesium, potassium, calcium, and alkanolamines) and the anion of the substantially saturated quaternary ammonium compound (i.e. chloride, bromide, iodide, sulfate) exchange, with their respective counter ions to form acids and/or salts and the resulting antimicrobial ethylenically unsaturated quaternary ammonium compound.
In a less preferred embodiment, the ethylenically unsaturated quaternary ammonium compounds of the instant invention my also be derived from primary, secondary and tertiary amines and known ethylenically unsaturated quaternizing agents, such as for example, vinyl chloride. Generally, such quaternizing agents include those agents which possess ethylenically unsaturated halides, ethylenically unsaturated alkyl sulfates, and the like, which are capable of effectuating a quaternaization of an amine to produce an ethylenically unsaturated quaternary ammonium compound with antimicrobial activity.
Accordingly, an improved method is provided for forming antimicrobial CASE materials and/or polymers, utilizing antimicrobial polymerizable surface active agents detailed herein. Generally, the improved method for preparing an antimicrobial CASE material comprising:
a) preparing a mixture comprising:
i) at least one ethylenically unsaturated monomer;
ii) at least one antimicrobial polymerizable surface active agent;
wherein the antimicrobial polymerizable, surface active agent is a ethylenically unsaturated quaternary ammonium compound derived from:
a) at least one acid, wherein the acid is a sulfonic acid, a carboxylic acid, or a phosphoric acid, or a salt thereof, or a mixture thereof, wherein the acid or the salt thereof contains at least one ethylenically unsaturated moiety; and
b) at least one substantially saturated antimicrobial quaternary ammonium compound;
b) polymerizing the mixture to form a latex or mixture of polymer particles;
wherein the antimicrobial polymerizable, surface active agent is capable of polymerization with the ethylenically unsaturated monomer or co-polymerization with a partially polymerized polymer particle. Somewhat preferably, the heteroatom of the acid is linked covalently, directly or indirectly, to the ethylenically unsaturated moiety of the acid. The method may further comprise the addition of optional ingredients as detailed herein, to produce a final antimicrobial CASE product.
The polymers prepared utilizing the polymerizable surface active agents of the present invention may be used as the primary resin component or a minor resin component of a resin mixture which is used to prepare antimicrobial latexes, coatings, adhesives, sealants, elastomers, binders, inks, floor finishes and the like. A polymer is defined herein as a product produced by polymerizing two or more monomers, which may be the same or different. Additionally, the polymer may have incorporated into it, surface active agent monomers and/or homopolymeric surface active agents. The various final antimicrobial CASE materials, compositions, applications and polymer products described herein may contain various optional ingredients such as fillers, pigments, colloids, colorants, solvents, plasticizers, antioxidants, curing agents, thickeners, non-polymerizable surface active agents (surfactants), preservatives, wet strength additives, and the like.
The present invention provides an improved polymerization process for forming polymers, wherein the polymerizable surface active agent used in the polymerization reaction does not interfere with the quality of the antimicrobial CASE materials. In many cases, the quality of the antimicrobial CASE materials is improved by the use of the antimicrobial polymerizable surface active agent.
The present invention provides an improved polymerization process, wherein antimicrobial CASE materials that are formed, using the polymers of the present invention, remain uniform and stable upon the passage of time and/or exposure to moisture at ambient or elevated temperature, once the CASE material is applied to a substrate. Additionally, the antimicrobial CASE materials possess extended antimicrobial activity, over long period of time and exposure to various deleterious elements, such as for example, water, solvents, washings with cleaning products, UV light, and the like.
The present invention provides antimicrobial polymers suitable for use in antimicrobial coating, adhesive, sealant and/or elastomer (CASE) materials. The polymers may be in a variety of forms, such as, for example, solids, flakes, powders, semi-solids, thick pastes, flowable/pumpable pastes (i.e. G-phase pastes), liquids, gels, xe2x80x9cringingxe2x80x9d gels, dilute or concentrated solutions and the like. The polymers may be spray dried, flaked, extruded, or the like.
The present invention additionally provides antimicrobial homopolymeric surface active agents comprised of polymerized, polymerizable surface active agents or blends of polymerizable surface active agents. These antimicrobial homopolymeric surface active agents are useful in the polymerization processes and antimicrobial CASE materials detailed herein. The present invention further provides antimicrobial homopolymeric surface active agent/polymerizable surface active agent blends comprised of partially polymerized, polymerizable surface active agents and non-polymerized, polymerizable surface active agents. These antimicrobial homopolymeric/polymerizable surface active agent blends are also useful in the polymerization processes and antimicrobial CASE materials detailed herein.
The improved polymerization process for forming antimicrobial CASE materials of the present invention preferably does not require the use of a surfactant which contains residual formaldehyde or other low molecular weight volatile organic compounds. However, while not desirable, low molecular weight volatile organic compounds, solvents and/or residual formaldehyde may be present in the polymerization products of the present invention. Further, the polymerization process of the present invention provides latexes useful in antimicrobial CASE materials with extended antimicrobial activity. Additional benefits of improved shear stability, improved pH stability, improved shelf storage stability and improved ease of viscosity modification may also be provided.
The antimicrobial polymerizable surface active agent may be added to the emulsion polymerization mixture in a batch mode (i.e. all at once), a continuous mode (i.e. by addition of an amount of the polymerizable surface active agent throughout the polymerization) or in a semi-continuous mode (i.e. addition of portions of the polymerizable surface active agent at various times during the polymerization). In a less preferred embodiment, the antimicrobial polymerizable surface active agent may be prepared in situ in the emulsion polymerization mixture, by adding at least one acid, wherein the acid is a sulfonic acid, a carboxylic acid, or a phosphoric acid, or a salt thereof, or a mixture thereof, wherein the acid or the salt thereof contains at least one ethylenically unsaturated moiety, to the mixture, followed by concurrent or step-wise addition of at least one substantially saturated antimicrobial quaternary ammonium compound, wherein the polymerizable surface active agent is formed in the mixture, with subsequent acid/salt formation.
The antimicrobial polymerizable surface active agents utilized in the present invention are generally formed by combining at least one acid, wherein the acid is a sulfonic acid, a carboxylic acid, or a phosphoric acid, or a salt thereof, or a mixture thereof, wherein the acid or the salt thereof contains at least one ethylenically unsaturated moiety; and at least one substantially saturated antimicrobial quaternary ammonium compound. The antimcrobial polymerizable surface active agents of the present invention are preferably in the form of quaternary ammonium compounds. The surface active agents of the present invention are prepared from readily available, economical raw materials, and generally, their preparation does not require any special handling or equipment.
The antimicrobial polymerizable surface active agents and blends of these surface active agents may be prepared in a variety of forms, including but not limited to, liquids, solutions, solids, powders, flakes, semi-solids, gels, xe2x80x9cringingxe2x80x9d gels, G-phase liquids, hexagonal phase solids, or thick pastes. The antimicrobial polymerizable surface active agents may be spray dried, flaked, extruded, and the like. Although not critical to the present invention, the antimicrobial polymerizable surface active agents may be prepared xe2x80x9cneatxe2x80x9d or in a conventional solvent such as water, low molecular weight alcohol or hydrocarbon, or a mixture thereof, to produce a solution of the surface active agent. The present invention encompasses antimicrobial surface active agents as quaternary ammonium compounds in dry form and as aqueous solutions. The antimicrobial quaternary ammonium compounds may be isolated by drying a solution of the surface active agents; a solution of surface active agents may be prepared by dissolving the quaternary ammonium compound in water, low molecular weight alcohol or hydrocarbon, or a mixture thereof.
Individual antimicrobial polymerizable surface active agents of the present invention may be prepared and mixed together to produce a surface active mixture comprising xe2x80x9cneatxe2x80x9d surface active agents or an aqueous surfactant blend. Additionally, neat or aqueous blends of the antimicrobial polymerizable surface active agents may be prepared by contacting a blend of two or more ethylenically unsaturated acids or salts thereof with one substantially saturated antimicrobial quaternary ammonium compound, or by contacting a blend of two or more substantially saturated antimicrobial quaternary ammonium compounds with a blend of 2 or more ethylenically unsaturated acids or salts thereof. Conversely, blends of the antimicrobial surface active agents may be prepared by contacting a blend of two or more ethylenically unsaturated acids or salts thereof, with one substantially saturated antimicrobial quaternary ammonium compound, or by contacting a blend of two or more ethylenically unsaturated acids or salts thereof, with a blend of two or more substantially saturated antimicrobial quaternary ammonium compounds. The antimicrobial polymerizable surface active agents useful in the present invention to form latexes, when used in a antimicrobial CASE material, such as for example, paint, printing ink, adhesive or pressure-sensitive adhesive, generally act as surfactants in the course of manufacture, storage or even processing thereof and, then, ceases to function as surfactants in due course thereafter. Furthermore, the antimicrobial polymerizable surfactants of the invention can be used not only as emulsifiers for emulsion polymerizations, but also as dispersing agents for suspension polymerization, dispersing agent for dyes and pigments, emulsifiers for waxes, finishing agents for fibers, emulsifier-dispersants for agrochemicals, antistatic agents for synthetic resins, and so on. In these and other applications, the aforementioned adverse effect of a residual traditional surfactant can be drastically reduced and/or eliminated.
These and other objects and advantages, as well as the scope, nature, and utilization of the claimed invention will become apparent to those skilled in the art from the following detailed description and claims.